fix(audit): Batch 7-9 dead_code 标注 + TODO 清理 + 文档同步

Batch 7: dead_code 标注统一 (16 处)
- crates/ 9 处: growth, kernel, pipeline, runtime, saas, skills
- src-tauri/ 7 处: classroom, intelligence, browser, mcp
- 统一格式: #[allow(dead_code)] // @reserved: <原因>

Batch 7+: EvolutionEngine L2/L3 10 个未使用 pub 函数
- 全部标注 @reserved: EvolutionEngine L2/L3, post-release integration

Batch 9: TODO → FUTURE 标记 (4 处)
- html.rs: template-based export
- nl_schedule.rs: LLM-assisted parsing
- knowledge/handlers.rs: category_id from upload
- personality_detector.rs: VikingStorage persistence

Batch 5+: Cargo.lock 更新 (serde_yaml_bw 迁移)

全量测试通过: 719 passed, 0 failed

Cargo.lock

@@ -1606,7 +1606,7 @@ dependencies = [
  "secrecy",
  "serde",
  "serde_json",
- "serde_yaml",
+ "serde_yaml_bw",
  "sha2",
  "sqlx 0.7.4",
  "tauri",
@@ -5913,19 +5913,6 @@ dependencies = [
  "syn 2.0.117",
 ]
 
-[[package]]
-name = "serde_yaml"
-version = "0.9.34+deprecated"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a8b1a1a2ebf674015cc02edccce75287f1a0130d394307b36743c2f5d504b47"
-dependencies = [
- "indexmap 2.13.0",
- "itoa 1.0.18",
- "ryu",
- "serde",
- "unsafe-libyaml",
-]
-
 [[package]]
 name = "serde_yaml_bw"
 version = "2.5.3"
@@ -7841,12 +7828,6 @@ dependencies = [
  "subtle",
 ]
 
-[[package]]
-name = "unsafe-libyaml"
-version = "0.2.11"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
-
 [[package]]
 name = "unsafe-libyaml-norway"
 version = "0.2.15"